1. Field of the Invention
The present invention relates to an apparatus and method for calculating satellite navigation visibility and, more particularly, to an apparatus and method for calculating satellite navigation availability in a ground transport environment using a sky view image.
2. Discussion of Related Art
When positioning is performed using a satellite navigation signal, an error in the positioning is affected by performance indices such as satellite navigation visibility, dilution of precision (DOP), a signal to noise ratio, and so on. In general, the performance indices are analyzed on a corresponding region before the positioning is performed using the satellite navigation signal, and then measurement is allowed to be performed when a predicted satellite navigation error is the least in the region.
The performance indices are highly utilized in a region where the satellite navigation visibility is good, for example, in an open area environment, and are less utilized in a region where there are many tall buildings, for example, in a ground transport environment. Accordingly, if a region is not the open area, the performance indices should be analyzed with a 3-dimensional topographic map of a measurement point. However, it is difficult to obtain the 3-dimensional topographic map, and even though the 3-dimensional topographic map is obtained, it takes a long time to develop a program for predicting the performance indices in the region using the 3-dimensional topographic map.
In the related art, a sky view factor (SVF) is calculated and used for environmental analysis. The SVF is a parameter indicating the extent of sky observed from a point as a proportion of the total visible sky hemisphere. For example, the SVF is equal to 0 if the sky is completely visible (for example, an open area), and the SVF is equal to 1 if the sky is completely invisible (for example, a sealed region).
However, as described below, the SVF indicates the extent to which the sky is visible or invisible, and has a limitation when utilized as a performance index for satellite navigation-based positioning.
Accordingly, a new parameter available for the environmental analysis is required in order to perform an accurate analysis, instead of or in addition to the SVF.